The present invention disclosed herein relates to a composition for forming a film having a wrinkle structure and a method of forming the film having the wrinkle structure.
Wrinkles are a common phenomenon in nature. A wrinkle structure may be generated at the skin layer during releasing the stress of the skin layer occurring when the double layer of a hard and thin skin layer and a soft and thick foundation layer contract. Here, the thick layer may act as a contractor of the double layer. For example, the skin of an apple may be considered as the skin layer, and the flesh of the apple may be considered as the foundation layer. When an apple is dried, the flesh may contract, and wrinkles may be formed at the skin of the apple.
Meanwhile, the size of the wrinkle structure of a film and the control thereof are significant technique in an organic light emitting diode (OLED). For the light extraction of the OLED, the period of wrinkle and the depth of wrinkle from about several micrometers to about several hundreds of nanometers are required. In addition, since the surface area increases depending on the wrinkle structure, the control of the wrinkle structure as a material for a sensor is significant. Wrinkle occurs due to a significant difference of elastic moduli between the skin layer and the thick layer. For example, the wrinkled film is produced in several tens of nanometers of metal layer on a thermally extended polydimethylsiloxane (PDMS).
Meanwhile, the inventors of the present invention have studied on a compound (prepolymer) for forming a film having a randomly ordered wrinkle structure (Korean Laid-open Patent Publication No. 10-2014-0016125). However, only curable compounds have been disclosed for forming a wrinkled film in previous studies, and the combination of the compounds with an appropriate photoinitiator and the principle on effective formation of a film with a wrinkle structure using the combination have not been disclosed. Further, various factors concerning the formation of a film with a wrinkle structure and the control of the size of the wrinkle structure (control of components of a solution, concentration of a vinyl group of a photo-curable agent and a photoinitiator, photo-curing rate, light intensity, and the thickness of a coated layer, etc.) have not been disclosed, either.